How long should a diesel engine last?

[pheran]

I'm sure this subject has been 'done' some time back but I can't find it. But it raised its head again in a more recent post when reference was made to an engine that had done 700 hours and an oil sample showed it was totally knackered and in need of a complete re-build. Surely, that must have been the result of extreme mistreatment/total lack of maintenance. If you consider 700 hours on a lorry at an average of, say 50mph, thats 35000 miles - barely run in! And that engine could reasonable expected to run on to 300,000 miles or more. So what does the panel think? Even accepting the 'harsher conditions' in which they are used, are boaters generally guilty of mistreating and prematurely ageing their engines?

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[duncan]

I was led to understand 10,000 hours was reasonable for an engine used frequently and responsibly in relation to my Yanmar 4LHA

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[philwebb]

I dont know what the ultimate lifespan of a diesel engine is but mine has been in
service for 35 years (Volvo MD5) . It had some major work 3 years ago -new
mainshaft seals, new injector sleeve, head skim and valve seatings recut, but
it starts easily and runs well . I did 2 return trips to Cherbourg under engine last
year. I think maintenance and regular oil changes keep engines going, also being
run under load at close to full revs is probably a good idea to get rid of carbon
deposits. I would guess that the end of the road for an engine is when you need
to do some major work and you can no longer get the parts.
Regards, Phil

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[gjgm]

recall some of the previous comments on this. Firstly comparison with a lorry isnt all that valuable, unless say with commercial boat engines where they are almost also in constant use. But the supposed average cruiser only completes 100 hrs per year. I d guess it also depends on how the engine is used. If you are talking about super high performance turbo'd engines that blasts tonnes of boat around the water, I'd guess its going to be knackered long before something ticking over hour by hour on a canal. DOnt they say most boat engines rot rather than break !

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[Deleted User YDKXO]

Its a myth that today's generation of lightweight turbocharged diesels are going to last as long as diesel engine plodders made years ago. Basically, today's marine diesel engines are highly tuned performance engines and in order to meet the boatbuilders demands for ever more powerful engines but with compact dimensions, engine builders are squeezing more and more power out of the same engine blocks with the result that many diesels are requiring major overhauls at less than 1000hrs. The more power you develop from a particular block, the shorter it's wear life will be
The engine manufacturer does'nt care because the likely failure will be well beyond the warranty period and will generate good spares and service turnover and the first owner of the boat does'nt care because he'll have sold the boat on well before any problems arise anyway. The real loser in this power race is the 3rd or 4th buyer of a boat who runs the risk of getting caught for major rebuild work
Basically, if you want your engines to last, go for naturally aspirated (non-turbocharged) engines or, if you've got to have turbo charged engines for planing performance dont choose the top power rated version of a particular engine model
Look at http://www.yachtsurvey.com/engines.htm for more info

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[MainlySteam]

<<<many diesels are requiring major overhauls at less than 1000hrs>>>

Cripes, I trust not. We are putting turbocharged diesels in new boats that will run 1,000 hours up in 3 months.

John

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[Deleted User YDKXO]

As I said, it depends on what type of turbocharged diesels and obviously wear is a function of age as well as operating hours and, of course, maintenance. What type of engines are you using and what are you putting them in?

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[kindredspirit]

There's a 42' Nelson next to me with one of its Cats "gone" after 290 hours ! !

Someone said it had been "hammered".

.

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[ParaHandy]

i'm not surprised because modern marine diesels are generating 75 and up bhp per litre which is an awful lot of power from a wee small pot ... did work on a boat with a long stroke gardner. could almost count the revolutions and it never failed (but it must have weighed tons) whereas the short stroke perkins wore the top of the bores out in a year

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[adarcy]

Agreed Deleted User

<<The more power you develop from a particular block, the shorter it's wear life will be>>

as a general rule but there's lots of buts.

It depends on the technology used eg old Beetles were supposed to last for ever but even when first introduced Golfs lasted better because of closer tolerances + better spec bearings etc despite much higher bore speed, piston accelerations and revs.
Cold starts kill engines, 90% of all engine wear ocurrs in the first 5 mins which is why high mileage reps cars, taxis and trucks "seem" to go on "for ever". Newer cars eg BMWs count the number of cold starts, engine revs and load when cold as well as overall running time in calculating when an engine service/oil chang is due. On our Merc it was about 12k miles in ordinary use and 18k when we used it on long continental trips one year.

New tech can be much kinder eg new common rail diesels have phased injection to reduce peak pressure loads on the pistons but then again the more fangled the injection setup with electronic control may give more trouble than the old-fashioned mechanical sort - especially in a marine environment.

Last + not least non-use ruins engines in a marine environment. A 100 hour/year boat engine has long periods for the bearings to dry out and corrode, it's much more hostile than a land environment

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[muchy_]

Mine too is around 35 years old and has been used extensively over that time. Two years ago it had a new crank and bearings so it's probably got another 35 years left in it.
However, I am having it changed next month for a modern engine because of the lack of spares now. Just hope the new engine is just as reliable and long lived as the old.

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[anchorhandler]

Sorry to jump here but one thing to consider is this:
When a diesel engine or even a petrol engine for that matter is running, there are very few surfaces that actually make contact. The main journals and crank pins will not be in contact with the shells but 'floating' in a film of OIL. During the stroke of the piston, the rings will accelerate and lift off the bore/liner of the block and skim over an OIL film (about 5 micron thick). The rings will touch the bore/liner at the bottom of the stoke and especially at the top when fireing pressures are developed forcing the ring pack outward, but luckily this is when the piston is moving at its slowest. The oil pump is continuously lubricated by oil when running, each lobe or gear seperated from the next by a thin film of OIL. Rockers and pushrod ends do make contact however they are splash lubricated and are not heavily loaded. Turbo bearings especially benefit from hydro-dynamic lubrication (shaft lifts clear of bearing and floats on film of OIL) due to the high revolutions. Fuel pump plungers act similarly to pistons and glide until at top or bottom stroke, lubricated by diesel OIL. etc.etc. The point is that OIL realy is the lifeblood of an engine and, for longevity of the engine, needs to be kept as clean as possible. Contaminents from the combustion process will inevitable dirty the oil rendering it black and it is this that needs to be kept in check!. oil filters usually only filter down to around the 30-40 micron size which is fine but if the oil isnt changed regularly, those contaminants will slowly erode away at the bearing shells as it passed through the finite clearences between shell/pin. The same thing happens to the piston rings, if the oil isnt clean, the rings (and dirty oil), will gradually wear away all the microscopic crevises on the liner/bore leaving it polished (or glazzed as some call it) These crevises retain OIL and allow the ring pack to lift up and slide. No crevices=no lubrication= rapid scuffing wear=$$$$.
Fuel also has to be treated in the same way as engine oil. it is imperative that no water gets into it otherwise rapid corrosion of pump internals will take place leading to rust contaminants which lead to plungers seizing. Keep the fuel as filtered as possible to avoid this problem and do use/check seperators regularly. Keep in mind water gets in in many ways, humidity/condensation in the fuel tank, leaking filler caps, loaded at source from the fuel barge etc...
Last point is the air that goes into the engine, unfortunately sea air contains a high concentration of sodium chloride (salt) and moisture which, when forced into an engine goes straight into the cylinger (poss through a turbo/intercooler) and makes a lovely microscopic grinding paste!...Fit a decent filter!.
I could go on and on but the points i have coverd above are the important basics, lookafter yor oil,fuel and air and your engine will look after you for many years to come. (how cheesy did that sound?) Oh and try not to overload it either!

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[MainlySteam]

I do concede that these are commercially rated engines and will also normally be only operated at max of 85% MCR. Without getting into previous boats and client's details the current new builds I was referring to each have 4 x 525kw engines each driving a water jet and are 35 knot (at 85% MCR) 23 metre power cats (high quality, aircraft type fitout, commercial passenger operation).

As you say, and the point I hoped would gather impetus, it gets down to the rating, the engine quality and maintenance regime. Many pleasure boat owners do not realise that their engines are max and non contiuously rated. Also, many new engines from reputable manufacturers are put into the pleasure boat market before being derated when poven and then put into the commercial one.

John

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[Deleted User YDKXO]

You've put your finger on it when you mentioned de-rating. Take the Cat 3126 engine which I happen to have in my boat. This is rated at 426hp (I guess this is an intermittent leisure rating) but the same engine for industrial use has a power rating of between 215 and 260hp (presumably continuous). Its no wonder that there is a huge difference in service life

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[pheran]

So how is this derating achieved? Is it just pump settings or what?

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[Deleted User YDKXO]

I guess its by remapping the electronic programme which controls the fuel pump delivery. I dont think its something that could be done as a DIY job

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[adarcy]

and often limiting the turbo boost pressure

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[anchorhandler]

The point to remember with your Caterpillars and any other engine for that matter is that, due to the increase in output, the frequency of services/maintenance will have to be increased!. More fuel in results in more power out, but at the expense of hotter exhaust gases flowing into your turbo's. The increase in peak pressures results in more stress at the piston crown and ring pack which will (after fatigueing sooner) need to be overhauled on a more frequent basis than a de-rated engine etc.etc.etc.
Look at it from the extreme point of view of formula 1, After one race, a 3 litre V8 race engine (developing what 500-650hp?) will require a complete stripdown and re-build because of the internal conponents being stressed to the point that they could fail.
Motorcruisers are much the same, an engine manufacturer will develop an engine with a high power to weight ratio which will allow the naval architecht to work out a theoretical top speed for his design of boat of 'x' kts. This high top speed looks great printed on the brochures and the marketing department love it too, but its unfortunately at the cost of a higher maintenance budget for the engines.
Its not that marine diesels will 'wear out' quicker its just that the maintenance regime has to be uprated! (keep in mind also marine engines work in a horrible enviroment)
And if you fancy de-rating your engines, the best way to do this is to have you fuel pump settings adjusted along with a nozzle/injector change. (if the engine is using a common rail fuel injection system then this can be 'tweeked' to allow less fuel per injection bur it is definarely not a DIY job) Serious de-rating where the power is significantly reduced will require more but there is no point in going into too much depth here.
Simon

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[Wiggo]

can you not achieve a similar derating by just leaning a little less firmly on the loud stick?

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[Deleted User YDKXO]

Marine engines do indeed wear out quicker precisely because of the points you have indicated. Typically, a construction machine engine will run to 10,000hrs without major overhaul providing it is regularly maintained. There's no way a modern high performance marine diesel engine will run to 10,000hrs without overhaul even if it is meticulously serviced
And typically a marine diesel is serviced more often than a construction machine engine, maybe once a season at 100hrs or so compared to every 250hrs or 500hrs or more for the construction machine so you could argue that the marine engine is better serviced.

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